The objective of the study is to evaluate the utility of extravascular lung water determinations by the thermal-dye dilution technique in a controlled clinical setting. All previous clinical studies published to date measured lung water only after the lung injury occurred. This study will use each patient undergoing major operative procedures with a high likelihood of inducing some form of pulmonary interstitial injury as his own control. Measurements will be made pre-operatively and sequentially post-operatively and compared for correlation with the standard available methods of measuring pulmonary function.